They don't look much like contemporary art-lovers. There are no sharp suits, silly haircuts or bold spectacle frames. Instead, the queue snaking outside the Royal College of Art (RCA) is made up of a motley group – bleary-eyed and unshaven – dressed in woolly jumpers and waterproof jackets.

They are there for the annual lucky dip. The prestigious college asks around 1,000 artists – from the famous to recent graduates – to donate up to six postcards of new work. Art-lovers can buy no more than four, at £40 each. The catch is that no one knows the name of their artist until after they have bought the work.

This year's coup was Gerhard Richter. The German, considered one of the world's greatest artists, painted six cards in his distinctive blurred abstract style. Other sought-after names included Grayson Perry, Anish Kapoor and Tracey Emin.

The doors open at dawn, and 50 raffle winners are given first dibs. Next come die-hard regulars, who have learnt that if you want to buy a contemporary great for peanuts, it's the very early bird who gets the work. By 7am the queue is wrapped around the RCA building in Kensington. Inside the RCA's white halls, it snakes across the wooden flooring and continues down a set of stairs past giant TV screens that reveal which works have gone and which are still available.

Buyers are busy scribbling in their notebooks as they try to keep up with the changing stock. Eventually, the queue winds its way to a cashier, who checks your choice is still available, takes your money, and gives you a form to take upstairs to the main gallery. There, rows and rows of postcards with a multitude of designs – drawings, paintings, photographs, inscriptions and collages – are mixed in with plain green cards to replace those that have been sold.

Chris and Gayle Corbett camped out and managed to be fifth in the queue. "We've been here for two and a half days," says Chris. "We love art. There's lots of people here during the night. You make friends, order a pizza, have a drink." They are hoping for a Nick Park or Tracey Emin. Their ritual, however, is not to open their envelope until after they've nipped off for a big breakfast. Others take their envelopes outside and open them immediately, frequently to squeals of delight.

Like hordes of others lining up for a card at the sale they had to register online first. Perry Hill, a solicitor, is in his 10th year at the sale, and very chuffed to find himself with a Grayson Perry drawing of a shoe as well as a Richter. "I thought it might be by Grayson because of the bow," he says. "I just love the sale. It's a real opportunity for people like me who can't afford to buy the artists that we like, to own their stuff."

Ms Bunn registered 5,000 new people for the sale this year, 2,000 more than normal. Some 14,000 had already registered over the sale's 16-year history. "There's 2,700 cards and we normally sell them all," she says. "Not everyone turns up and not everyone buys four. We invite around 3,500 artists and this year 1,016 agreed. I first asked Richter in 2007, and his studio said he would be interested but was busy. I never let go. He couldn't do it last year, but this year he painted six, and sent a note saying it was a great project."

By 1pm the queue is shorter, although latecomers are still tagging on. The last person – for now – is Heather Broughton who has travelled from Leicester. "There is something very British about queueing," she says. "I'm not bothered about anyone famous: it's about the future. I work for a museum in Leicestershire, which has been buying new art to loan to schools for 50 years. It now has work by people like Bridget Riley and David Hockney."

Finally, after what seemed like a lifetime of queuing, The Independent on Sunday gets to buy a work. It's by the Welsh artist Carwyn Evans. By now Chris Corbett has had plenty of time to savour his purchase. He calls, having finished a leisurely breakfast, to reveal the couple's days of vigil has been rewarded with a card by the fashion designer Manolo Blahnik. His tone bears the quiet satisfaction of a modest lottery winner. "We're very pleased," he says simply.